D  

Standard lateral cephalograms are produced with the patient about 15–18 cm in front of the film, so X-ray beam divergence enlarges all linear dimensions; most cephalostat set-ups give roughly 8-12 % magnification, commonly rounded to “about 10 %” compared with the true cranial size. Studies measuring skulls directly versus their cephalograms confirm this ~10 % enlargement factor (e.g., magnification factors of 1.06–1.13 reported by Dibbets & Nolte 2002 and up to 14 % for long mid-sagittal distances in Olmez 2011) [Dibbets & Nolte 2002, PMID 12165775; Olmez 2011, PMID 21261485]. Hence the cephalogram is approximately 10 % larger than the actual cranium.